Method of dispersing keratin proteins with amides and the composition resulting therefrom



Patented July 1a, 1948 UNITED STATES PATENT orr cs amnion or DISPERSING xaria'rrn Pao- :rsnzs wrrn AMIDES AND 'rnn comosr- HON ansum'ma rnnnnmom Chase B. Jones, Waltham. Mass, and Daie x. Meohsm, Richmond, CaliL, assisnors to the United States oi America as represented by the Secretary of Agriculture No Drawing.

application November I, 1944, Serial No. 562,326. Divided and this appiication May a, 1941. Serial No. new

Claims. (01. 100-155) (Granted under the act of March 3, 1883, amended April 30; 1928; 370 0-6-157i ing keratin proteins obtained from a keratin neutral or practically neutral reaction, and at relatively =1ow temperatures. These conditions produce less degradation of the'original keratin than occurred in the prior art and the dispersed keratin maybe recovered in a form substantially similar'to that of the original keratin in regard to its composition, isoelectric point, solubility, and other properties.

The method'involved in this invention is based partly onthe reduction, of the disulflde bonds within the'keratin molecule by treating it with sulfur-containing, reductive disuliide-splitting material such as feathers. hoofs, horns, wool,

and so forth, and has among its objects the use of such keratins, either in the dispersed or recovered forms. in the preparation of artificial fibers, films, plastics and the'like.

Keratins, like the more solubleproteins, can be readily dispersed by hydrolysis in strong acids or alkalis, but the keratin thus dispersed cannot be recovered except as simple degradation products, such as amino acids or complex degradation products, such as peptides, peptones, and proteoses, the properties of which differ radically from those of the original keratin.

Keratins can also be dispersed in alkaline solutions of metallic sulfides and such sulfides are commonly used in cosmetic depilatories and in the removal of hair from hides in the tanning industry.

\ which produced drastic degradation of the proteins.

Also, keratins may be dispersed in strong alkaline solutions by treatment with reducing agents,

and the recovered protein is more similar to the original protein in regard to solubility, molecular size, and so forth, than are the peptides; proteoses, etc., referred to previously. However, the I presence of the strong alkali is undesirable because it presents an opportunity for the hydrolysis of the keratin, destruction of the cystine constituent of the keratin (keratins being unique among proteins in that they contain exceptionally large amounts of cystine), and destruction of the hydroxy amino acid residues of the keratin.

According to our invention, keratin materials are dispersed under mild conditions, that is, in

agents such as monoethylene thioglycol (thicglycol), thioglycolic acid (present as the thinglycolate in neutral solution), and sodium bisul- The presence of alkali is obviated by the use of any of a number of protein-denaturing or protein-dispersing' agents, such as urea, guanidine hydrochloride, ammonium thiocyanate, formamtically neutral reaction.

Therefore, under the above conditions of employing disulphide-splitting and protein-dispersing orprotein-denaturing agents to eflect the dispersion in neutral or practically neutral reaction and at relatively low temperatures, the keratin molecule undergoes minimal degradation, the only chemical attack-on the covalent linkages oi the keratin being the cleavage of the disulflde bonds of the cystine moiety.

The following examples are illustrative of our invention:

Example I 1.4 parts of monothioethylene glycol and 27.2 parts of guanidine hydrochloride are dissolved in water. Sodium hydroxide solution and water are then added as required to obtain parts oi solution at about pH 6.9. 2.5 parts oi. cattle hoof filings are treated with this neutralized solution in a water bath at about 40 0. about for 18 hours. The mixture is stirredat convenient intervals. During this period about 74% of the hoof keratin is dispersed in the solution; After removal oi in] for the preparation of artificial fibers.

the undispersed hoof by filtration, the dispersed keratin may be precipitated either by dilution with several volumes of water, by salting out with M3804, (511102804, etc., by acidification, or by dialysis. If desired, the guanldine may be removed from the dispersion by dialysis and may be recovered from the dialysate by precipitation as the nitrate or by other suitable means.

Example I] 1.1 parts of NaI-ISO: and 21 parts of urea are dissolved in water. Sodium hydroxide solution and water are added as required to obtain 35 parts of solution at about pH 7.1. 2.5 parts of wool are treated with this solution in a water bath at about 40 C. about for 18 hours, during which period'the mixture is stirred at frequent intervals. wool is dispersedby this treatment. The dispersed wool may be precipitated and recovered from the solution either by dialysis, by salting out with MgSO4, (N114) 2504, etc., or by careful addition of a suitable amount of acid or alkali.

Example HI pH 6.8. This solution is heated to boiling and 64 parts of chicken feathers are added. The solution is kept boiling gently for about 30 minutes with frequent stirring. During this period considerable dispersion of the feathers occurs and. the undispersed portion becomes very soft and loses its original shape. 200 parts of boiling water are now added and the solution is boiled and stirred for about another 30 minutes. The undispersed residue is removed by suitable filtration and is washed several times in hot water. The washings and filtrate may be combined and evaporated to dryness to obtain '70 parts of a water-soluble product that has been found use- This material contains 8.5% to 8.6% nitrogen on a dry basis.

' Example IV of the solution is about 6.0. The solution is heated 52% of the original weight of the persed by this treatment.

to boiling and 80 parts of chicken feathers are Example I! 1.6 parts of thioglycolic acid and 21 parts of urea are dissolvedin watery Sodium hydroxide solution and water :are added as required to obtain parts of solution at about pH 7.0 (10.2) 2.5 parts of duck feathers are added, and the mixture is heated at about C. for about 18 hours. About 78% of the feather keratin is dis- Example V1 1.4 of monothioethylene glycol and 24 parts of ammonium thiocyanate are dissolved in water. Sodium hydroxide solution and water are added as required to obtain 35 parts of solution having a pH of about 6.9. 2.5 parts of chicken feathers are treated with this solution for about 18 hours at about 40 0. During this period about 82% of the feather keratin is dispersed.

Example VII 1.4 parts of-monothioethylene glycol and 20.7 parts of acetamide are dissolved in water. Sodium hydroxide solution and water are added to "give 35 parts of solution having a pH of about 1.4 parts .of monothioethylene glycol and 27.2 parts of guanidine hydrochloride are dissolved in water. Sodium hydroxide solution and water are added as required to obtain 35 parts of solution having a pH of about 7.0. 2.5 parts of hog hair are added and the mixture is heated at about 40 C. for about 18 hours. About 56% of the hair is dispersed during this period.

In addition to the foregoing examples, many other experiments were performed, the results of which are shown in the following tables:

Tum: I

Dlspersibilities of keratin: in dfflerent dispersing agents upon reduction by 0.5 M thioglycol [2.5 g. of keratin was treated for 18 hours atabout 40 C. with 35 ml. of solution at pH 7] Guanilorm- Aeet- Synthetic l Kerstin dine n01 gaig amide amide Detergent (8.1 M) (10.0 M) (10.0 M) (10%) Per cent Per cent Per cm! Per cent Per cent Per cm! 1 Chicken feather... 84 82 66 59 10 70, 80 Duck mama.-." 83 so 41 36 6 51, 53 Tortoise scutes 64 52 10, 8 Snake skin 55 44 26, 30 Cattle hooi 74 56 7 6 5 58, 64 Wooli 61 36 4 6 4 44, Cattle horn.-- 36 27 3 5 4 14, 12 Hog hair 56 26 2 2 2 4, 3 Human hair-. 50 11 0 0 2 2, 1 Ovokeratin 8 6 4 3 15 2, l

1 Composed of sodium alkyl suliates.

First values calculated from dry weights of residues after acetone extraction; second v lue mlml w rom i ws mlrm v I'll-III Dispersibilities of keratin: in M urea upon reduction by difierent disulfide-spiittino agents [2.5 g. of keratin was treated ior 18 hours at about 40 C. with 36 mloi solution at pH 7] NIHBOI Th Thioglyoolic Kerstin Percent eaSBBSSBtiS ass-ass es Many changes and variations in the conditions for dispersion shown in the foregoing examples and tables may be made. As a rule, the

higher the concentration of protein-dispersing or protein-denaturing agent, the greater is the percentage of keratin dispersed, the solubility of the dispersing or denaturing agent being a limiting factor. A greater degree of dispersion may also be obtained in some cases by increasing the concentration of the disulphide-splitting agent, as for example, for monoethylene thioglycol and thioglycolic acid. An increase in the concentration oi NaHSOs, however, often results in a decrease in the extent of dispersion of the keratin. presumably due to a salting-out eflect.

Also, it is not necessary in every case that the solution be near the .point or neutrality (pH 7.0) For example, the dispersibility or human hair in a solution of thiogiycol and sodium salicylate is increased as the pH of the solution is increased about from 6.9 to 11.4. The use of neutral solutions merely minimizes the possibility of hydrolytic degradation of theprotein which may be detrimental in some cases. It the pH is increased above about pH 10, dispersion occurs it only a disulphide-splitting agent is present: however, the presence of a protein-dispersing or protein-denaturins agent, as used in our invention,

permits dispersion below pH 10.

The temperature at which dispersion, according to our invention, is obtained may range up to about 100 C., and the higher the temperature within this range, the shorter the time required for dispersion, and in some cases. a higher degree of dispersion is obtained. Therefore, it is recommended that the invention be conducted at a temperature range of up to about 100 C.

Having thus described our invention, we claim:

1. The process comprising heating a keratin material in an essentially neutral aqueous solution containing a sulfur-containing, reductive disulphide splitting agent and a member of the group consisting of urea, thiourea, iormamide, acetamide, and urethane at a temperature up to about 100 C. to disperse said keratin material in said solution.

2. The process comprising heating a keratin material in an essentially neutral aqueous solution containing sodium bisulphite and urea at a temperature up to about100 C. to disperse said keratin material in said solution.

3. The process comprising heating a keratin material in an essentially neutral aqueous solution containing thioglycolic acid and urea at a temperature up to about 100 C. to disperse said keratin material in said solution.

4. The process comprising heating a keratin material in an essentially neutral aqueous solution containing monoethylene thioglycol and acetamide at a temperature up to about 100 C. to disperse said keratin material in said solution.

5. A, composition of matter consisting essentially or a dispersion of a keratin material in an essentially neutral aqueous solution containing a sulfur-containing. reductive disulphide-splitting agent and a member or the group consisting of urea, thiourea, .formamide, acetamide. and urethane.

6. A composition of matter consistingessentially or a dispersion or a keratin material in an essentially neutral aqueous solution containing sodium bisuliite and urea.

CHASE B. JONES. DALE K. MECHAM. 

